The invention relates to a device for use in retrieving an object that falls in water or in saving a person who falls in water, whereby the device is provided with means for attaching the device to the object to be retrieved or means with which the person to be saved can carry the device with him, respectively, (and provided) with a spray water-resistant holder that comprises a mechanism for opening of the holder, which holder in its closed state encompasses an empty, inflatable body of a substantially gas-impermeable matter in a folded state, and with one or more reagents which react under the influence of water that has entered the holder to form a gas, which gas serves for filling the folded inflatable body in order to exert a flotation or driving force on the object attached to the device or on the person carrying the device.
A device for use in retrieving an object that falls in water is known from the French patent publication FR-2733482. This known device is cylindrical-shaped and it comprises a disc which at one of its surfaces is provided with a tube that extends perpendicularly with respect to the disc surface. The diameter of the tube is smaller than the diameter of the disc. The assembly of the disc and tube is surrounded at the side of the free end of the tube by a cover which has a mainly cylindrical form and of which the diameter is slightly larger than that of the disc, and of which the height is greater than that of the tube. The cover at its open end facing the disc fits well around the disc, thus encompassing the tube on the inside of the cover. The disc at its circumference is attached to the cover with the aid of means that open when these come into contact with water, in this case the means are formed by plugs of sodium chloride. The disc at its side facing the interior of the cover, and thereby lying within the diameter of the tube, is provided with a number of openings which connect the inside of the tube to the outside of the disc and the device. The openings, too, are provided with closure means that open when they come into contact with water, in this case the closure means are also plugs of sodium chloride. The bottom of the tube that is provided with the openings on the side of the disc is filled with a tampon of surgical cotton, a strong and hydrophilic material. There is a reaction body at the top side of the tampon, in the interior of the tube, which consists of a matter that, when it comes into contact with water, undergoes a chemical reaction and thereby forms a gas. In the known device it is calcium carbide which reacts with water to form acetylene and calcium hyroxide. The inside of the tube at its end facing away from the disc is closed with a grating that keeps the tampon and the reaction body packed together against the bottom of the tube. There is an inflatable bag provided at the free end of the tube. The opening of the bag, which is in a closed state, is attached to the outside of the free end of the tube. In a resting state, the folded bag in the inside of the cover lies around the tube. Finally, there is also a ring on the outside of the cover for attaching the device to the object to be retrieved, in this case a key.
The operation of the known device is as follows. When the object to be retrieved in question, such as a key, falls in water, then it sinks due to its mass. Because the key has a higher density than that of the device, the key comes to hang on the underside when it sinks. During the sinking, the plugs of sodium chloride which connect the disc and the cover to each other, dissolve in the water. The plugs of sodium chloride which connect the openings between the disc and the interior of the tube provided within the cover, to each other also dissolve in the water. This allows water to enter in the tampon and the water is absorbed by the tampon. The reaction body thus comes into contact with water by means of the tampon. Gas is created through the above-mentioned reaction, with the gas escaping through the grating to the inflatable bag to thereby fill the bag. The tampon serves two functions, namely absorbing the water that comes into the tube and—especially while water is being absorbed in the tampon—restricting that the formed gas escapes from the bag or the tube through the openings in the disc to the outside. During the sinking of the object in the water, whereby the disc hangs underneath because of the key which hangs on the disc, the disc detaches from the cover, thereby also aided by the pressure exerted by the formed gas. When sufficient gas has been formed and the bag has inflated sufficiently with this gas, a flotation force arises that allows the key hanging on the disc to rise to the surface.
A disadvantage of the known device relates to the cover. The volume of the cover on the one hand should be sufficiently large to be able to contain a sufficiently large bag and on the other hand be small and lightweight since it will come to hang on the object to be retrieved.
Because the bag that is to be stored in the cover must not be too large, this aspect also lays a limit on the flotation power which can be effectuated through the known device. As such, only small, light weight objects can be floated with it.
Another disadvantage of the device relates to the speed with which the device can come into action. Under certain circumstances, such as when sailing, there is a risk that the inflatable body will be unnecessarily inflated. The openings in the disc which are closed with plugs of sodium chloride, can lose their closing function at conditions of sufficient atmospheric humidity, since sodium chloride is hygroscopic. There are also objections against the use of acetylene, the gas that provides for the flotation or driving force, with the known device. A mixture of acetylene and oxygen is explosive, acetylene is toxic and it also has an unpleasant odour. Another disadvantage relates to the durability of the operability of the device, considering that acetylene is very sensitive in regard of humidity.
Another disadvantage of the known device relates to the valve function with which entry of water in the cover is regulated. This valve function is provided by a number of parts, namely the plugs of sodium chloride with which the openings have been closed and the tampon on the inside of the tube which absorbs the water entering through the openings. If the tampon for whatever reason is drenched insufficiently by which the entering water does not or not sufficiently reach the reaction body, then the reaction will not start or propagate, respectively, so that the intended operation will not occur. The tampon acts as a water barrier when water is taken up in it. So some of the formed gas always diffuses through the tampon and through the openings to the outside. If the tampon thus does not absorb sufficient water across the whole of its breadth, then the eventually formed gas will escape along the tampon and the openings in the disc on to the outside.